Patent publication WO 2009/083017 discloses such a radar apparatus. It is known that radar measurements can be used for detecting a life-sign of a subject, such as respiration and heart beat. Radar measurements are a robust alternative to other contactless life-sign monitoring systems, e.g. based a magnetic field sensors or capacitance sensors. By performing a contactless life-sign measurement, people can automatically be monitored, e.g. infants, older people or patients.
In operation, the transmission electromagnetic beam is directed to the chest and/or the abdomen of the person to be monitored, in order to receive a reflected beam including information of breath and heartbeat.
It appears, however, that it is very difficult to reliably extract heart beat in the presence of breathing from the reflected radar signal.